Heathrow closure

The shutdown could cost the airport, the airlines that operate from it and the businesses that rely on them tens of millions of pounds, business correspondent Paul Kelso reports from Heathrow. But the airport and the government may pay a bigger price in the damage to their reputation, he says - just a few weeks ago, they were talking about building a third runway at Heathrow to boost economic growth, but yesterday they couldn't even run the ones they've got... Watch Kelso's full report on the economic impact of the shutdown

Sky News' helicopter has being flying over the deserted airport. Footage filmed from the air shows how quiet the usually bustling travel hub is. Dozens of planes remain at standstill and runways are empty.

Passengers are stuck in "no man's land", travel expert Simon Calder has warned. He describes the situation as "absolutely awful for so many," with passengers facing the "appalling situation" of trying to re-plan their journey. He explains the airline is "absolutely responsible" for providing a hotel, giving you meals and getting you to your destination if you're a flying on a British or European airline out of Heathrow. "The people you need to be concerned about are those flying in from the outside Europe," he tells our presenter Anna Jones. "Those airlines, because they're not British, do not have any obligations when they are flying to the UK from their home countries." "An awful lot of passengers are not even planning to spend any time at Heathrow. They just want to connect through. And let's just take, if we may, the flight from Accra in Ghana, which is currently on the ground in Lille in southern France. "Lovely place, but if you're one of the many Ghanaian passengers, there is a pretty good chance that you won't necessarily have permission to enter France because you weren't expecting to be there. "At which point they are going to be stuck in a kind of no man's land. Waiting in the transit lounge until something can happen to them." Calder says questions will be raised over how a critical piece of national infrastructure can be put out of action. "I'm going to hope that what Heathrow did by saying it will close until midnight tonight, that they did that out of an abundance of caution, and let's hope they do have the systems up and running," he adds.

Today's closure of Heathrow Airport is "a full crisis management situation," an aviation industry analyst has said. Speaking to our presenter Anna Jones, Sally Gethin said: "They will be going through emergency procedures because obviously a substantial fire like that, even though it's not actually on the airport site itself, poses a risk as well. "There will be a number of evacuation emergency procedures that will come into play today for Heathrow." Turning to the challenges the airlines face in a situation like this, Gethin said "they split themselves in two". "They'll have the one side that will be dealing purely on the ground and collaborating, working closely with Heathrow and emergency services... and the other side will be dealing with the aircrews." Watch the full interview in the video below...

The substation fire that forced the airport to close has been described as "really unusual" by an energy expert. "It looks like the extent of the fire has damaged some of the equipment," Tim Green told our presenter Anna Jones, adding the airport would have multiple electrical routes as well as backup generators. Green said the substation was "one of the large ones in the country" and at least one of its three transformers, key parts of the substation, has been "very badly damaged". He explains the transformers take a long time to order, and it's unusual to carry a stock of those, meaning it will likely take a long time to repair the damage to the substation. Watch the full interview here...

We reported at 8.52am on Adeel Anwar telling Sky News what he witnessed firsthand this morning. The driver described the aftermath of the substation fire, and the chaos it caused, as "absolutely apocalyptic". Watch the full interview below

Our correspondent Sadiya Chowdhury is outside Heathrow Airport this morning, where she says the skies are "completely silent". She explains the closure is likely to cause "massive disruption" for anyone travelling today, but those living nearby have also been affected. "Lots of homes had to be evacuated, this happened during the night so many people would have already gone to bed by that time," Chowdhury says. She adds there's a cordon in place, with a lot of disruption for homes and businesses in the area. Chowdhury also points out that those travelling to Heathrow today will be affected by road closures and the fact no Heathrow Express services are running in either direction. Watch her update from Heathrow Airport below...

Energy Secretary Ed Miliband tells Sky News there was a backup generator but that it was "also affected by the fire". He says it shows "how unusual and unprecedented" the situation is. And, he adds, it is "too early to know" what caused the substation blaze. Describing it as a "catastrophic fire", Miliband says he has spoken to the National Grid about the situation. He adds that his heart "goes out" to those impacted but that he is "reticent to jump to conclusions" about what has happened.

We've been reporting Heathrow Airport is closed today due to a fire at a nearby substation which caused a major power outage. Watch this drone footage below showing the North Hyde electricity substation engulfed in flames.

Heathrow Airport was plunged into darkness after a major power outage caused by a fire at a nearby electricity substation. "It's all dark here, mate" one person said while recording the empty terminal. Watch the scene from inside one of Heathrow's terminals below...